Resilient File System (ReFS) overview

In this article

The Resilient File System (ReFS) is Microsoft's newest file system, designed to maximize data availability, scale efficiently to large data sets across diverse workloads, and provide data integrity by means of resiliency to corruption. It seeks to address an expanding set of storage scenarios and establish a foundation for future innovations.

Key benefits

Resiliency

ReFS introduces new features that can precisely detect corruptions and also fix those corruptions while remaining online, helping provide increased integrity and availability for your data:

Storage Spaces integration - When used in conjunction with a mirror or parity space, ReFS can automatically repair detected corruptions using the alternate copy of the data provided by Storage Spaces. Repair processes are both localized to the area of corruption and performed online, requiring no volume downtime.

Salvaging data - If a volume becomes corrupted and an alternate copy of the corrupted data doesn't exist, ReFS removes the corrupt data from the namespace. ReFS keeps the volume online while it handles most non-correctable corruptions, but there are rare cases that require ReFS to take the volume offline.

Proactive error correction - In addition to validating data before reads and writes, ReFS introduces a data integrity scanner, known as a scrubber. This scrubber periodically scans the volume, identifying latent corruptions and proactively triggering a repair of corrupt data.

Performance

In addition to providing resiliency improvements, ReFS introduces new features for performance-sensitive and virtualized workloads. Real-time tier optimization, block cloning, and sparse VDL are good examples of the evolving capabilities of ReFS, which are designed to support dynamic and diverse workloads:

To deliver both high performance and capacity efficient storage, ReFS divides a volume into two logical storage groups, known as tiers. These tiers can have their own drive and resiliency types, allowing each tier to optimize for either performance or capacity. Some example configurations include:

Performance tier

Capacity tier

Mirrored SSD

Mirrored HDD

Mirrored SSD

Parity SSD

Mirrored SSD

Parity HDD

Once these tiers are configured, ReFS use them to deliver fast storage for hot data and capacity-efficient storage for cold data:

All writes will occur in the performance tier, and large chunks of data that remain in the performance tier will be efficiently moved to the capacity tier in real-time.

If using a hybrid deployment (mixing flash and HDD drives), the cache in Storage Spaces Direct helps accelerate reads, reducing the effect of data fragmentation characteristic of virtualized workloads. Otherwise, if using an all-flash deployment, reads also occur in the performance tier.

Note

For Server deployments, mirror-accelerated parity is only supported on Storage Spaces Direct. We recommend using mirror-accelerated parity with archival and backup workloads only. For virtualized and other high performance random workloads, we recommend using three-way mirrors for better performance.

Storage Spaces with SAS drive enclosures

Integrity-streams, online repair, and alternate data copies enable ReFS and Storage Spaces to jointly to detect and correct corruptions within both metadata and data.

Storage Spaces deployments can also utilize block-cloning and the scalability offered in ReFS.

Basic disks

Deploying ReFS on basic disks is best suited for applications that implement their own software resiliency and availibility solutions.

Applications that introduce their own resiliency and availability software solutions can leverage integrity-streams, block-cloning, and the ability to scale and support large data sets.

Note

ReFS is supported with Storage Spaces, Storage Spaces Direct, and non-removable direct attached drives. ReFS is not supported with hardware virtualized storage such as SANs or RAID controllers in non-passthrough mode. USB drives are also not supported.

Feature comparison

Limits

Feature

ReFS

NTFS

Maximum file name length

255 Unicode characters

255 Unicode characters

Maximum path name length

32K Unicode characters

32K Unicode characters

Maximum file size

35 PB (petabytes)

256 TB

Maximum volume size

35 PB

256 TB

Functionality

The following features are available on ReFS and NTFS:

Functionality

ReFS

NTFS

BitLocker encryption

Yes

Yes

Data Deduplication

Yes

Yes

Cluster Shared Volume (CSV) support

Yes

Yes

Soft links

Yes

Yes

Failover cluster support

Yes

Yes

Access-control lists

Yes

Yes

USN journal

Yes

Yes

Changes notifications

Yes

Yes

Junction points

Yes

Yes

Mount points

Yes

Yes

Reparse points

Yes

Yes

Volume snapshots

Yes

Yes

File IDs

Yes

Yes

Oplocks

Yes

Yes

Sparse files

Yes

Yes

Named streams

Yes

Yes

The following features are only available on ReFS:

Functionality

ReFS

NTFS

Block clone

Yes

No

Sparse VDL

Yes

No

Mirror-accelerated parity

Yes (on Storage Spaces Direct)

No

The following features are unavailable on ReFS at this time:

Functionality

ReFS

NTFS

File system compression

No

Yes

File system encryption

No

Yes

Transactions

No

Yes

Hard links

No

Yes

Object IDs

No

Yes

Short names

No

Yes

Extended attributes

No

Yes

Disk quotas

No

Yes

Bootable

No

Yes

Page file support

No

Yes

Supported on removable media

No

Yes

NTFS storage tiers

No

Yes

See also

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